The CoreMap key identifying the offset of the last character after the end
of an annotation. The character with index 0 is the first character in the
This key should be set for any annotation that represents a span of text.
Returns the type associated with this annotation. This method must
return the same class type as its value type parameter. It feels like
one should be able to get away without this method, but because Java
erases the generic type signature, that info disappears at runtime.